Photographic shutter



Sept. 19, 1950 F. P. wlLLcox ,5

PHOTOGRAPHIC SHUTTER Filed Oct. 17, 1946 3 Sheets-Sheet 1 7 o L 3 .57 52m w 54 3 55 IN VEN TOR. FREDERICK F2 W/L LCOX P 1950 I F. P. WILLCOX2,522,698

7 PHOTOGRAPHIC SHUTTER Filed Oct. 17, 1946 3 Sheets-Sheet 2 IN VEN TOR.FREDERICK F. W/LL COX A T TQRNE rs Patented Sept. 19, 1950 UNITED STATESPATENT OFFICE PHOTOGRAPHIC SHUTTER Frederick P. Willcox, Vestal, N. Y.,assignor to General Aniline & Film Corporation, New York, N. Y., acorporation of Delaware Application October 17, 1946, Serial No. 703,906

exposures and so constructed that its power mechanism functions in astraight line pathway.

Among the objects of the invention is that of devising a shutter whichwill provide, along with the slower speeds, high speeds substantiallygreater than any now available in commercial, between-the-lens typeshutters.

It is a further object todevise such a shutter which shall have aminimum mass for those parts which move during exposure, and in whichthe construction shall be greatly simplified and its manufacture andassembly facilitated by the employment of power mechanism movable in astraight or right line pathway.

It is a further object to devise such a shutter in which the masterelement shall cause the blades to be opened and closed by a cammechanism, the cam pathway of which follows a constantly accelerated anda constantly decelerated curve both in the opening and closing phases.

It is a further object to devise a shutter of this type in which theblades shall be opened and closed by a cam as above stated and in whichall parts shall be simple in design and construction, yet in which themovement shall be effective and efficient in combination with extremeruggedness and dependability of operation.

It is a further object to provide in such a shutter a right linemovement for the master member and other parts of the power or mastermechanism in which a supplemental spring may be brought into play bymechanism selectively operable at the higher shutter speeds,

A further object of the invention is that of providing bladeinterconnecting means adjustable at assembly and at desired timesthereafter for synchronizing the positions and movement of each of theblades during opening and closing thereof and for taking up any slackdue to wear after a period of use.

It is a further object of the invention to employ very thin blades andto reenforce those blades at their pivotal points so as to provideadequate strength and resistance to wear after repeated use withoutmaterially adding to the inertia to be overcome as the shutter functionsin opening and closing the blades.

It is a further object of the invention to devise a shutter mechanism inwhich the blades shall be controlled positively throughout the entirecycle of movement and to prevent reboundat the end of the stroke, bothat the end of the opening and the closing movements.

It is a further object of the invention to devise means whereby themaster member shall be checked during bulb exposures thereby to preventundue strain on the operating and control mechanisms.

It is a further object to construct a compact shutter of the typedescribed in which the actual operation shall conform to the besttheoretical mode of functioning, by designing the cam action so that itshall combine with the lowering of spring tension during release,friction and in-- ertia forces, to bring about that desired end.

A further object is that of providing for the retard mechanism aresilient construction by which the shock of the first contact betweenthe moving shutter mechanism and the retard means is absorbed.

Another object of the invention is that of providing means to preventundesired opening of the shutter blades as the power mechanism is primedor cooked.

Other objects will become apparent as the description proceeds.

The invention is herein described and illustrated as applied to abetween-the-lens type shutter in which the master member is set prior toexposure and wherein release is effected by the usual trigger or byremote control means which may be interconnected for operation on atrigger or the like. Such a shutter is of the symmetrical opening typeand may employ any suitable number of blades from three to a greaternumber depending upon the size, cost, and other factors.

The entire mechanism is housed within a casing of general annular shapeand comprises a priming or cooking means, blades, blade interconnectingand operating mechanism, a master member including a rectilinearlymovable cam and a power means such as a, spring to impart the motionthrough the cam to the blades. The power or master mechanism isengageable by mechanism by which it may be controlled to determine thetype of exposure, for example, instantaneous, bulb, or time exposures.The duration of exposure is controlled by a train of gears, a sectorgear and a pallet, the function of which and the specific mode ofoperation of which will be more clearly described in later paragraphs.

As the master member is moved to cocked position, there would be, ifspecial provision were not made, an undesired opening and closing of,

the blades. Mechanism later to be described is provided for preventingsuch undesired exposure at that time. The details of the above-mentionedmechanism will be more thoroughly described by reference to theaccompanying figures of drawing, wherein like parts are indicated bysimilar reference numerals and wherein:

Fig. 1 is a view showing parts of the shutter with the front of thecasing removed.

Fig. 2 is a perspective view, slightly exploded, showing theinstantaneous, bulb and time levers and the trigger.

Figs. 3 and 4 are detail views of the master member.

Fig. 5 is a view similar to Fig. 1 but showing only part of the face ofthe shutter broken away and including the retarding mechanism which hasnot been shown in Fig. 1.

Fig. 6 is a detail view of the disconnecting means which functions whenthe shutter is primed.

Fig. 6a is an enlarged detail of part of the mechanism of Fig. 6.

Fig. '7 is a view showing the blade interconnecting and operating means.

Fig. 8 is a detail of the cam pathways for the speed setting ring.

Fig. 9 is a detail of one link of the blade interconnecting means.

Fig. 10 is a view showing a modification in which a supplemental springis employed for actuating the master member.

Fig. 11 shows a speed setting ring for use with that modification inwhich a supplemental spring is employed.

Figs. 12 and 13 are details of the control mechanism for selectivelyemploying the supplemental spring of Fig. 10.

Now referring to Fig. l, the shutter is housed within a casing whichincludes a, generally cylindrical outer member H] which is rectangularlyformed at its lower side by the projecting angular parts H. The powermechanism is housed at the said lower or rectangular portion of thecasing and, in the interest of conserving space, the general circularform of the casing is thus modified. However, if desired, a slightlybigger casing of circular outline might be employed, thereby simplifyingthe pressing of the casing but sacrificing in the size thereof.

A plurality of shutter blades l2 are pivoted as shown more clearly inFig. 7, the blades herein numbering four, but it is to be understoodthat any suitable number may be employed. These blades are positionedbehind a transverse wall l3 and in front of the rear wall I4 as is theusual custom. Each of the blades is pivoted at a point l5 and ispreferably of extremely thin sheet material thereby to cut down the massand keep inertia forces as low as practicable. To strengen the blades attheir pivotal areas, a plate designated by numeral [6 is riveted theretoby the rivets IT, or is connected to the blade in any other satisfactorymanner. Each of these reenforcing plates has two projecting arms l8 bywhich the blade is caused to swing about its pivot I5 for opening andclosing it and these arms are in turn interconnected by links I9, thenumber of which will naturally correspond to the number of blades. Theselinks will be described in greater detail as the disclosure progresses.While the general arrangement for interconnecting blades is not novel inthis case and may be observed in United States Patent No. 1,626,032, itis believed that the links by means of which the blades areinterconnected for actuation are novel per se and that the method bywhich these links may be initially adjusted as to length and by whichlater adjustments may be made to take up for possible wear is new anddescribed herein for the first time.

At the center of the shutter assembly, the annular space within thecasing is defined by the cylindrical ring or wall 20 within which is theusual lens carrying or mounting member 2|, that being conventional and,therefore, forming no part of the present invention.

The power mechanism housed within the easing and positioned by the lowersomewhat rectangular part thereof includes a sheet metal retainingmember 22 between the ends of which is fixed a spindle or guide-rod 23along which may slide freely the master member generally designated bynumeral 24. The spindle also carries the power member or spring 25. Itis to be understood that the spring 25 is considerably longer than whenuntensioned and that there is considerably initial tension in the springeven before moving the parts to their cocked or primed position.

A ring 26 is freely movable about the inner cylindrical part of thecasing 20 and has thereon a, nose portion 21, cam 28, and the priminglever 29 which extends through slot 30 to the outside of the casing tobe engaged by the operator in the usual manner. A spring 3| normallyretains these parts in the position of Fig. 1.

The master member 24 is shown in greater detail in Figs. 3 and 4 and ispreferably formed by pressing sheet material to a rectangular box-likestructure cut away as at 32 at its sides for the purpose of lighteningthe structure. The end portions 33 and 34 have therein circular openings35 and 36 which are a working or sliding fit on the spindle 23. A camslot 3'! is cut at the back face of the master member and may be dividedinto four different portions, later to be dezcribed in detail. The sidematerial at the point 38 projects forwardly of the spindle 23 to aslightly greater extent than at the opposite end and that top projection33 serves as a surface against which the nose 2! of the priming membermay engage during the priming movement. The retaining member 22 ispreferably fixed in the casing mem ber [G by suitable screws or otherattaching means. The attaching wall of the casing I0 is slotted toprovide a slight amount of adjustment. When properly adjusted, theretaining screws are tightened down thereby solidly locking the powerunit in position. The action of the cam on its follower would naturallygive rise to forces tending to rotate the master member about thespindle 23. To prevent such undesired movement, the master member hasits back surface (that in which the cam slot is cut) in contact with thecooperating side of the retaining member 22, and since these engagingfaces are ground to a suitable bearing, the friction of the parts is notgreat, while the tendency for rotation above mentioned is prevented.

Now referring to Fig. 4, the cam slot 3'! is laid out as shown, themovement from cocked position to released position being understood tobe from left to right. The ends of the path which are subtensione'd. Theleft hand end of the cam pathway designated by numeral 40 holds theblades closed when the mechanism is in its released position. Thatportion 4| of the cam slot marked "Blades opening functions to open theblades and this part of the slot first follows a constantly acceleratedpathway and then a constantly decelerated pathway. The central portion42 of the pathway designated by the term Blades open is substantiallystraight and merely functions to hold the blades in open position forthat period of time necessary depending upon the speed at which theshutter is set. The following portion 43 marked Blades closingcorresponds to the Blades opening portion except that it is more or lessa reversal thereof, the first portion following a constantly acceleratedcurve and the second a constantly decelerated curve after which theblades remain closed as the short straight portion of the pathway 48governs.

"The terms constantly accelerated and constantly decelerated have beenused and the cam path has been calculated to give that desired type ofmotion for the blades. Since friction and inertia of the parts as wellas the fact that the spring naturally loses tension as the master membermoves to the right, Fig. 1, are to be considered, the actual curvatureof the cam path is not a theoretically perfect one. The above-mentionedfactors are taken into consideration and the blades themselves areopened as nearly as practicable with the desired constant accelerationand are closed with nearly a constantly decelerating motion. Of course,with the number of variables which must be considered, no particularshutter can be expected to function with the theoretically precisemovement. That movement is approached as nearly as possible under thecircumstances.

Now referring to Figs. 1, 4, 6, 6a, and 7, the blade mechanism is causedto pass through its cycle of movement under the influence of a pivotedplate or lever 44 capable of being swung about a pivot pin 45 by theaction of the cam slot 31 which engages a projecting pin or follower 48.The plate 44 has pivoted thereto at 41 a link 48 which in turn engages apin 49 which is a special one of the pins by means of which one of thelinks I8 is connected to its arm 18. A spring 58 tends to swing the link48 in a direction so that it will engage the pin 49, although the samemay be intentionally disengaged therefrom since the pin enters a slot atthe top of the link. Such disengagement is effected each time the mastermember is moved to cocked position in a manner hereinafter to bedescribed. The pin 49 extends through wall L3 to engage the cam slot.

The priming ring 26 has a cam 28, Fig. l, which engages one end of ashort lever pivoted at 52. A spring 53 tends to keep the cam engagingend of the lever down against the ring 26. The opposite end of lever 5|is bent angularly as at 54 and engages the top end of a more or lessvertically disposed bar 55 which is slidable as provided by the slots 56and 51 which engage about the pins 58 and 59. A spring 80 tends tomaintain the bar in its uppermost position. The first slight angularmovement of the priming lever 29 causes the cam 28 to lift thecooperating end of lever 5! thereby to push downwardly the bar 55 sothat the lowermost end thereof which is forked as at 6|, will engage thetop of link 48 and push it down against the tension of the spring 50.That initial movement takes place just before the nose 2] projectingfrom the priming ring 26 engages the projecting abutment 38 of themaster member. At that time, the forked end 6|, the pin 49, and thenotch 62 in the link 48 are all in alignment as shown in Fig. 6. As thelink 48 is pushed down so that notch 82 is disengaged from pin 49, thenose of the priming means engages and then moves the master member tothe left, Fig. 1, the cam therein causing the link 48 to move to theright as in Fig. 6a. and then back to its initial position when themaster member has become latched in its fully cooked position. At thattime, the priming lever 29 is released and the spring 3| will naturallyreturn it to its initial position. The lever 5| drops from cam 28 andbar 55 rises to disengage the link 48 and to permit reengagement of thenotch 82 with pin 48. The mechanism just above described preventsunintended opening and closing of the shutter blades during the cookingmovement.

Now referring to Figs. 1 and 2, a series of latching levers is provided,these levers being pivoted at 63 on a suitable pivot means which passesthrough the holes 64 located about at the center of these levers. Thelowermost or shortest ones of these levers designated at is providedwith a latching or hooked end 66, and at its opposite end has aturned-up or angularly projecting extension B'l. This lever controls themaster member 24 for instantaneous exposures, and also, in connectionwith the other levers, provides for the initial release during bulb andtime exposures. A trigger 68 is pivoted at 69 and comprises a more orless extended portion adjacent the pivot from which project theshoulders or lever engaging portions 10 and H. The usual manuallyengageable trigger extends through the case I0 and serves to release theshutter. A flat angularly disposed plate member 12 provides for shutterrelease by a cable.

The second or time lever 13 has a latch 14 and at its opposite end anupturned angular projection 15 of greater length than the projection 61.The topmost lever 16 which is the bulb lever has a corresponding latch17, an angular projection 18 for engagement by the shoulder H, then ashort parallel portion '19 terminating in the projection 88 of similarlength to and extending parallel to the projection 15.

The shoulders 18 and TI on the trigger engage against the extensions 61and 15 for shoulder 18, and against extension 78 for shoulder I I. Theprojection 88 and the outer end of projection 15, as will hereinafter bedescribed, are engaged by a cam in the speed setting ring by means ofwhich the instantaneous, bulb, and time exposures are set. Of course,the extension 61 is always engaged by the shoulder 18 and release of themaster member is always first effected by the lever 65. During thecooking movement, the nose 2'! moves the master member 24 to the leftslightly farther than is necessary for engageent of the latch 68 withthat master member. A spring 8! coiled about the stud 82 to which thespring 8| attaches bears against the extension 6'! so that the lever 65always tends to remain in a position to keep the master member latchedas shown in Fig. 1.

The time lever 113 is also urged by means of a spring 83 to a latchingposition except as that lever is retained in inactive position bymechanism hereinafter to be described. Similarly, a spring 84 urges timelever 76 to a latching position except as retained in inactive positionin a manner similar to that employed for the lever Now referring to Fig.5, the retarding mechanism will be described. This retarding mechanismcomprises a sector gear 85, a series of intermeshing gears and pinionsgenerally designated by numeral 86, driven from the sector gear anddriving at the end of the train a star wheel 8?. The star wheel 8? isengaged by a pallet 88 pivoted at 8% at one end of a two-armed lever 93pivoted at 9! and having a projecting pin 92 at the end of the oppositelever arm for engagement with a cam pathway in the speed setting ring. Aspring 93 is coiled about the ivot SI, engages one of the lever arms anda fixed point in the casing thereby to bias the assembly in suchdirection that the pallet will normally engage the star Wheel.

Sector gear is pivoted at 94 and rather than permit the sector itself tocontact the master member, the sector is, in effect, resilientlyconstructed as a two-part member, one of which engages the master memberto impart motion derived therefrom to the sector through a resilientmeans. The resiliently connected contact element 95 is also pivoted at 9and has a projecting nose which, when desired, is engaged by a themaster member 24. This member 95 imparts its motion to the sector gear85 through a spring 9? coiled about a grooved pin 98 and projectingdownwardly at each end into an appropriate hole, one in the sector gearand the other 1 in the member 95. A spring 93 coiled about the pivot 9 iengages the sector gear at a fixed surface in the casing to urge thesector gear assembly in a clockwise direction or in such direction thatit would tend to be engaged by the master member at an early point inthe travel of the latter. The retaining casing 22 is folded inwardlyadjacent the sector gear as at H13 and serves as a stop for the gear 85and member 95 as they are moved in the clockwise direction under theinfluence of spring es.

Now referring to Fig. the speed setting ring is shown at idi it beingunderstood that most of that ring lies behind the front face I02 of theshutter casing. Outside that face I62 may be rotated the outer portionI83 of the speed setting ring which is serrated as is the usual practiceand on which are the usual graduations including the time and bulbsetting marks and the speed indications from 1 second to 230 of asecond, or such other indicia as may be applicable to the particularshutter to which the invention is applied. These speed indications areset opposite an index or fiducial mark on a plate I54, Fig. 5.

At the right hand side of the speed setting ring, Fig. 8, is a cam slothavin the inner surface thereof defined as a cam pathway against whichthe pin or follower Q2 on the pallet withdrawing means bears. The firstpart of this cam pathway designated by numeral I85 removes the palletfrom engagement with the star wheel for time and bulb exposures. Thesecond or depressed part of the pathway 103 permits the pallet to moveinto engagement with the star wheel for the lower shutter speeds, forexample, for speeds of one full second to 1 -0- of a second. Theremainder of the pathway at till causes the withdrawal of the pallet forhigher shutter speeds, e. g., of a second to the maximum.

The next cam pathway serves to control the position of the sector gear85 and, of course, the position of the nose 9% of the attached,resiliently mounted contact element 95. The pin 98 projects sunicientlyfar beyond the operating mechi f u L) anlsm to extend into thecontrolling slot in the cam ring and bears against a cam surface at theouter part of that slot. While the pallet is withdrawn during time andbulb exposures, the remainder of the retarding mechanism is permitted toexert its full effect upon the master member for the purpose ofabsorbing some of the energy built up during the initial movement ofthat member after its release by the lever 65 and before it is stoppedby the bulb lever Hi. The position of the parts is such that the mastermember 24 engages the projection or nose 96 and is retarded in itsmovement as the retarding train runs practically throughout its maximumextent of travel prior to engagement of the master member by the latchI1. That lessens the shock on the mechanism during time and bulbexposures. The part of the pathway designated by numeral 18 permits thefull effect of the train to be exerted at that time.

For the slower instantaneous speeds, the pallet is brought intoengagement and the cam surface I09 properly positions the sector gearand train so that the requisite amount of retarding influence will beexerted. For the faster speeds, th pallet is again withdrawn and allcontrol, if any, is exercised through the gear train itself the positionof which is determined by the cam surface H0.

The position of the time and bulb levers is controlled by the third camslot in the speed ring and the inner portion of that slot governs thefirst or depressed part III permitting the levers I3 or I6, or both ofthem, to drop to a position in which they may engage the master member.For a bulb exposure the projection 88 drops to the surface I I I,thereby permitting lever I6 to swing to a position in which the latch Ilmay engage and stop the master member as the blades reach their openposition. For time exposures, the speed setting ring is moved to thelimit of its clockwise travel so that both projections i5 and drop tothat surface III. For all instantaneous exposures, both levers arewithdrawn and, therefore, both projections ride upon the cam pathway H2.

Referring more specifically to Figs. 10, 12, and 13, a modification ofthe invention is shown in which a supplemental spring comes into actionfor higher or faster shutter speeds. Like numerals with primes areemployed for the parts of the shutter which correspond to similar partsabove described with respect to the preferred form thereof. In additionto the parts previously described, there are provided the supplementalspring II3, a spring retaining cup II4 having a flange H5, and a latchmember IIS. This latch member is shown in greater detail in Figs. 12 and13 and includes a flat spring arm II'I riveted to the retaining member22 which is curved outwardly to provide additional space as at I I8. Thelatch I I6 has the side pieces I I9 and a front wall I20 which isinwardly bent to engage the flange II5 on the cup H4. The side wall I20is bent to extend forwardly and downwardly at I2I, thereby providing aramp for deflecting the latch downwardly to permit latching engagementof the flange cup as shown in Fig. 10. When the supplemental spring isto be employed, the latch ismoved to disengaged position by contact of apin I22 with a cam slot in the speed setting ring.

The springs II3 and 25' are wound in reverse directions so as to preventinterference between the coils thereof. The cup I I4 slides freely alongthe outer surface of spring 25' and the initial tension in the spring II3 is such that it exerts considerable force even when the cup H4 bearsagainst the master member 24' in its right hand position, Fig. 10.

The pin I22 engages within a cam slot I2 which is actually out in thelower or inner surface of the speed setting ring I02, and morespecifically, at the outermost or graduated ortion I03 thereof. Themajor portion of the cam slot I23 permits the latch I I6 to engage thecup I I4 and thereby hold the supplemental spring in its inactiveposition. At that time, the shutter may be cocked and will functionunder the tension of the spring 25 just as described with respect to thefirst-mentioned form of the invention. For speeds from /200 to /600 of asecond, for example, the position of the speed setting ring is such thatthe left hand end of the cam causes'the pin I22 to withdraw the latchfrom the cup thereby releasing it. Then, upon release, the master memberis caused to move by the combined tension of both springs. Upon thefirst cocking movement after a release of the spring H3, and uponsetting the speed ring at a lower shutter speed, the spring will belatched in active position. Speeds may also be changed so as to releasethe supplemental spring for action after the shutter is cocked, or aftercocking the shutter at a higher speed, the speed ring may be rotated torelease the latch I I6 whereupon the cup H4 will be held and th springrendered ineffective.

Now referring to Fig. 9, a connecting link !9 is shown in detail. Thisconnecting link has been bent to form a series of waves I24 for thepurpose of shortening the link and effecting an adjustment thereof, andconsequently, an adjustment of the blades, the position of which isgoverned by the links. A tool having complementary surfaces which arepressed together against the sides of the link serves to form the wavesI24 and the extent by which the link itself is shortened may be variedby the degree of bending effected by the tool. This adjustment is of useas the mechanism is initially assembled, and, of course, is resorted tothereafter for correcting any lack of synchronization between thevarious shutter members and for taking'up for lost motion due to wear orother causes. This method of adjustment and the design of the linksthemselves makes it unnecessary to work to close limits in forming thelinks or in positioning the plates IBand their arms I8 with respect tothe blades I2, Fig. 7.

Operation The shutter is set for making an exposure by first setting thespeed ring at the particular speed and type of exposure desired. Forexample, the ring may be set at an instaneous exposure from one fullsecond to /600 of a second for the particular shutter illustrated. Thepallet and the position of the sector gear 85 will be adjusted accordingto the time of the exposure and, since it is to be an instantaneous one,the cam pathway H2, Fig. 8, will have moved both the levers I3 and I toa position in which they have no effect upon the master member 24.

The shutter is cocked by moving the projecting lever 29 clockwise as faras it will go thereby moving the master member to the left, Fig. l, tobe latched by the instantaneous lever 65. Release by pressing downwardly0n the trigger 68 will engage shoulder II! with extension 6'! and willwithdraw latch 66 from in front of the master member. The spring 25 willthen move the master member to the right first opening the shutterblades, then engaging the retard mechanism to latch IT as for a bulbexposure.

10 time the exposure (except at the fastest speed) and thereafterclosing the blades. The position of the retard mechanism and of thepallet 88 determines the duration for which the blades remain open orthe amount of time it takes for the master member 24 to move the extentof the flat portion 42 of cam 31. For the fastest exposure, no contactbetween the master member and the nose 96 of the resiliently connectedblade 95 is permitted.

If the modification shown in Fig. 10 is to be employed, the setting ofthe speed will involve selective employment of the supplemental spring IHim the higher speeds.

For a bulb exposure, the speed ring is set with the letter B oppositethe index and at that time the pallet is withdrawn and the retardingtrain is set to exert its greatest retardinginfluence on the mastermember. The position of the speed setting ring is such that the lever 16is permitted to drop to a position to stop the master member before theshutter blades start to close. At that time, the projection will havedropped to the lower pathway I I I of the cam, Fig. 8. The mechanism isset as before, and upon releaseby pushing down on trigger 86, the latch66 is withdrawn permitting movement of the master member to the rightuntil it is stopped in mid-position by latch l I on the bulb lever, Theretarding means functions to slow up the movement of the master memberjust before it is stopped by the latch IT thereby absorbing some of theshock which would otherwise have to be taken by that mechanism. Theblades remain open so long as the trigger is held down but upon releasethereof, the spring by which it is returned to initial position willcause the trigger to move clockwise and the shoulder II to engage theportions I8 of lever I6 thereby to withdraw the latch 11 and permit themaster member to complete its movement thereby closing the blades.

For a time exposure, the mechanism is appropriately set so that both theprojections I5 and 80 drop to the cam edge III thereby to permit boththe time and bulb levers '13 and I6 to move to a position for latchingthe master member. The retarding train is likewise set in its fullyeffective position. The mechanism is cocked as before and upon releasethe. master member moves to that point where it stops against the Thetrigger 68 may then be released whereupon the bulb lever is withdrawnpermitting the master member to move a slight distance until it is againengaged and stopped by the time lever. A second movement of the triggerbrings shoulder I0 into contact with projection 15 for withdrawing thelatch 14 and permitting the termination of the exposure by furthermovement of the master member to the right.

Conclusion The invention has been described by reference to a preferredembodiment thereof, but changes may be effected, such, for example, asthat of substituting for the levers I8 and the connecting links I9,other mechanism which might take the form of the more conventional bladering having a projection such as the projection 49 which might engagewithin a notch in the link 48, Fig. 6a. Then actuation of the link bymechanism as herein described would impart motion through the blade ringto the blades.

The master member has been illustrated here as slidable on a spindle andas being guided by one face of the retaining member in which the mastermember and power mechanism are held. Obviously, variations may beresorted to and other means for guiding the elements in their slidingmovement along a straight line may be employed. In some shutters themovement of the master member may be in other than a horizontaldirection and its force may be applied at some other point about theshutter mechanism. While coil type compression springs have beendescribed and illustrated here, the master member may be moved bysimilar springs under tension, or may be affected by other means forimparting the power impulse necessary.

While one form and a modification of the invention have been disclosed,it is to be understood that the inventive concept may be carried out ina number of ways. This application is, therefore, not to be limited tothe precise details described, but is intended to cover all variationsand modifications thereof falling within the spirit of the invention andthe scope of the claims.

I claim:

1. In a camera shutter of the type described, the combination of acasing, a plura ity of shutter blades movable to and from open andclosed positions to effect an exposure, means interconnected to saidblades and angularly movable for imparting the said opening and closingmovements to the blades, and means engageable with said meansinterconnected to the blades for imparting the said angular movements toit which incudes a master member having therein a cam means comprisingopening and closing portions between which is a dwell, said openingportion following a constant acceleration and then a constantdeceleration curve and said closing portion following similar constantacceleration and deceleration curves, means upon which said master member is moved in a right line pathway, a power means to urge said mastermember in one direction, said power means comprising springs, onetelescoped within the other, and latch means by which the outermost ofsaid springs may be selectively retained in an inactive position, alatch means to hold the master member in primed position and a triggerfor releasing said latch means.

2. In a camera shutter of the type described, the combination of acasing, a plurality of shutter blades movable to and from open andclosed positions to efiect an exposure, means interconnected to saidblades and angularly movable for imparting the said opening and closingmovements to the blades, and means engageable with said meansinterconnected to the blades for imparting the said angular movements toit which includes a master member having therein a cam means comprisingopening and closing portions between which is a dwell, said openingportion folowing a constant acceleration and then a constantdeceleration curve and said closing portion following similar constantacceleration and decleration curves, means upon which said master memberis moved in a right line pathway, a power means to urge said mastermember in one direction comprising a spring under compression forbiasing said master member in one direction, a second spring telescopedabout the first said spring and similarly under compression for biasingsaid master member, a spring retaining means and a latch member adaptedin one position to engage said spring retaining means and to hold saidsecond spring in a compressed, inactive position thereby to permitactuation of said master member by the first-mentioned spring only, andmeans for disengaging said latching means thereby to permit said secondspring to engage said master member and, upon cocking said master memberand releasing it, to exert its force thereon in addition to that of thefirst spring, a latch means to hold said master member in primedposition, and a trigger for releasing said latch means.

FREDERICK P. WILLCOX.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 444,083 Ba-usch et al. Jan. 6,1891 607,242 Huff et al July 12, 1898 1,626,032 Fairchild 1. Apr. 26,1927 1,861,257 Barenyi May 31, 1932 2,269,400 Steiner Jan. 6, 19422302,401 Strassenburg Nov. 17, 1942 2,326,077 Steiner Aug. 3, 19432,362,546 Fuerst Nov. 14, 1944 2,371,072 Simmon et al Mar. 6, 9 52,382,624 Fuerst Aug. 14, 1945 2,397,546 Harris Apr. 2, 1946 2,398,567Transfers Apr. 16, 1946 FOREIGN PATENTS Number Country Date 686,453France Apr. 14, 1930

